Sea levels have risen about 20cm in the South West Pacific since the late 19th century, a new scientific study shows.
Sea levels in Tasmania remained relatively stable for much of the past 6000 years but around 1880 they started rising drastically, said Dr Patrick Moss from the at .
Between 1900 and 1950, relative sea level rose at an average rate of 4.2 mm per year.
鈥淥verall the rate of 20th century sea level rise reconstructed from our data is 1.5 mm per year,鈥� said Dr Moss, who co-wrote a on the study with scientists from (UK), the (NZ), (UK), the and (UK).
The highest rates of sea level rise occurred in the 1910s (.3 - .8 mm per year) with a second peak in the 1990s.
鈥淭he rise in 1910 probably reflects the end of the little ice age, when temperatures were about one to two degrees cooler in the northern hemisphere than today,鈥� Dr Moss said.
鈥淭he 1990s peak is most likely indicative of human-induced climate change.鈥�
The study used sediment cores from Tasmania鈥檚 salt marshes to reconstruct a record of past sea levels.
鈥淭he surface of the marshes builds up over time in response to tidal inundation, providing an accurate record for sea level change,鈥� Dr Moss said.
鈥淪ea level observations in Australia only go back as far as European settlement.
鈥淏y comparing our measurements to official observations we can look at long-term changes in sea levels.鈥�
Sediment layers in the core samples also provided physical evidence of the start of logging in Tasmania, when nuclear testing was at its peak globally, and the introduction of unleaded petrol.
Dr Moss said an accurate measurement of past sea levels had significant implications for understanding sea level rise under a changing climate.
鈥淎ny drastic changes from the norm, which persist for several decades and over a wide area, represent important climate signals,鈥� Dr Moss said.
鈥淭his in turn has implications for where we build our cities and infrastructure.鈥�
The results of the study, published in , indicate that the magnitude of sea level rise is much higher in the South West Pacific than elsewhere on the planet and that this could be attributed to ice-melt from sources in the northern hemisphere.
鈥淎 large ice-melt is like a fingerprint,鈥� Dr Moss said. 鈥淲hen such a significant mass shifts around the earth鈥檚 surface we can detect its movement.
鈥淏ased on this, it appears likely that the primary source of sea level rise in the Southern Hemisphere is the Greenland Ice Sheet, but also mountain glaciers in Alaska, western North America and the Canadian Arctic.鈥�
The group of scientists will do further research in Tasmania and the South Island of New Zealand, with the aim of creating a more complete picture of the extent of sea-level rise in the South West Pacific.
Media: Kate Swanson, , ph +61 7 3346 7406; Dr Patrick Moss, ph +61 7 3365 6418, mobile 0438 128 770. Copies of the article can be provided 鈥� not for redistribution.
